A method used for repairing pipelines and other structures includes the use of a liner tube having a felt layer on its inside and having a protective layer made of polymer or other plastic material on its outside. The liner tube is vacuum-impregnated with a resin mix in what is commonly referred to as a “wet-out” process. Just prior to wetting-out the liner, a catalyst is mixed with the resin so as to activate the resin and cause it to begin curing and hardening. The resin impregnated liner tube is then inverted into the pipeline so that the felt layer is inverted from the inside of the tube to the outside. Once the resin cures and hardens, the liner provides a new lining for the pipeline. Some resins are set to cure at ambient temperatures. In some instances, steam or hot water is applied inside the lining tube to speed the cure time
One problem with the method is that the catalyst must be mixed with the resin before the liner tube is wet-out and before positioning the liner tube at the damaged section of pipe. Once the catalyst is applied to the resin, the resin begins curing and time is of the essence in order to have the liner tube in place within the pipeline to be repaired. If the resin hardens before the liner tube is properly positioned within the pipe, it may require that a portion of the existing pipeline be dug up and replaced. If, on the other hand, a resin mix with a longer cure time is used to ensure adequate working time to install the liner, productivity suffers as the crew waits for the liner to cure and harden.
Aside from the loss in productivity, there are also additional costs involved in retarding or accelerating the cure time. For example, following the wet-out process the lining tube can be packed in ice and stored in a refrigerated compartment of the truck to retard or prevent the resin from curing. To accelerate the cure time, a large boiler and other equipment is required at the job site. Such equipment and the associated labor required all add to the total installation cost.
Use of a pre-formed liner tube itself can be problematic. For example, the liner tube is normally fabricated off-site in a factory and thus the dimensions of the host pipe and the section of pipe in need of repair must be known in advance to construct a liner of appropriate size. Conventional liners are also susceptible to shrinkage and other structural problems.
Some attempts have been made to spray or sling grout onto the interior surface of the pipe. Such methods are also problematic. Spraying or slinging grout inside the pipe does not provide for a uniform wall thickness of the lining. The grout or other material applied will also tend to run away from the crown of the pipe and toward the bottom of the pipe before the material can cure and harden. This sagging effect results in the uneven distribution of lining material around the interior of the pipe. The lining also does not have a smooth surface. Still further yet, the spraying or slinging method is not effective in areas of the pipe where there is ground water infiltration.
In addition, at times the grout or resin must be pumped a long distance prior to being sprayed or slung on the wall. To be able to pump the material the required distance, the viscosity of the grout or resin material must be low enough to not become clogged or otherwise prevent the movement of the material. However, a material of such a viscosity would sag or fall off of the interior wall of the pipe or structure, as noted above. In addition, most resins or grouts require mixing of two parts to cause the material to begin to cure. Thus, two separate dispensing tubes must be provided so that the two parts of the material do not mix and begin to cure, which would prevent pumping of the material.
Therefore, there is a need in the art for a method and apparatus for pumping a curable material a long distance, which overcomes the need for a pre-formed or resin-absorbent liner, and that also overcomes the problem of the material sagging or not sticking to the wall of the structure.